This invention relates to a high-retention sanitizer composition that can be applied to surfaces in a variety of forms. In particular, this invention relates to aqueous sanitizer compositions comprising one or more antimicrobial agents, characterized by improved retention time on surfaces to be sanitized.
Aqueous solutions of antimicrobial agents such as lower organic peracids, especially those comprising peracetic acid, are effective as sanitizer compositions against a wide spectrum of microorganisms, including algae, fungi, bacteria, and viruses. However, because both concentrated and dilute solutions of lower organic peracids have a viscosity close to that of water, i.e., about 1 centipoise (cP), the solutions are not retained when applied to certain irregular and/or non-horizontal surfaces. On surfaces on which water does not readily spread, such as stainless steel, plastic, and foods such as vegetable produce and fruits, and the fatty regions of animal carcasses, the sanitizer composition tends to bead up and run off, instead of spreading uniformly over the surface. If the retention time of the sanitizer composition with the surface could be increased and the sanitizer composition were to spread evenly over the surface instead running off, the effectiveness of the sanitizer composition should be increased.
Because peracid and other antimicrobial solutions are frequently used as sanitizer compositions for food and for food machinery, as well as on non-food contact surfaces, it is essential that the method of increasing the contact time be non-toxic and environmentally friendly. In addition, the method of increasing the retention time should not catalyze decomposition of the antimicrobial agent or otherwise adversely affect its ability to sanitize the surface to which it has been applied.
Retention time can be increased by increasing the viscosity of the solution. However, this normally requires the addition of large amounts of other materials, which increases the cost of the sanitizer composition. Thus, a need exists for a method of increasing the retention time of organic peracid and other antimicrobial agent containing sanitizer compositions on surfaces, especially on irregular and/or non-horizontal surfaces as well as on surfaces on which water does not readily spread, that does not use materials that are toxic or leave undesirable residues, that does not markedly affect the stability of the antimicrobial agent, and that does not greatly increase the cost of the sanitizer composition.
In one aspect, the invention is an aqueous composition (A) suitable for use as a high-retention sanitizer composition, especially on irregular and/or non-horizontal surfaces as well as on surfaces on which water does not readily spread. The composition (A) comprises:
a) water;
b) about 1 ppm to about 3000 ppm of an antimicrobial agent; and
c) a retention aid comprising about 0.01 wt % to about 3.0 wt % of a mixture of a non-ionic surfactant and an anionic surfactant; and, optionally,
c) a magnesium ion source;
in which:
the non-ionic surfactant has a polar non-ionic group attached to a first alkyl having 8 to 20 carbon atoms;
the anionic surfactant has an anionic group attached to a second alkyl group having 8 to 20 carbon atoms; and the ratio of the non-ionic surfactant to the anionic surfactant is about 0.1:1 to about 0.4:1.
The first and second alkyl groups typically are straight chain alkyl groups substituted on the terminal carbon atom (1-position) with the polar non-ionic and anionic groups, respectively. Preferably, the first and second alkyl groups have substantially the same number of carbon atoms.
Another form of the sanitizer composition of the invention is a composition (B) comprising:
a) water;
b) about 1 ppm to about 3000 ppm of an antimicrobial agent;
c) a retention aid comprising (i) about 0.025 wt % to about 1.0 wt % of a biopolymer thickening agent and (ii) about 0.01 to 3.0 wt % of at least one surfactant; and, optionally,
d) a magnesium ion source;
in which the composition has a viscosity of about 3 cP to about 15,000 cP. Suitable biopolymer thickening agents include polysaccharides and heterpolysaccharides as hereinafter described. The surfactants used in the retention aid of composition (B) may be the same or different from those used in the retention aid of composition (A).
In other aspects, the invention includes retention aid concentrates, packaging of the sanitizer composition as a multi-part kit, and a method for sanitizing a surface by application of the composition to the surface, for example, as a foam. In the kit, a first part may comprise an aqueous solution of the antimicrobial agent and a second part may comprise the retention aid concentrate.
In sanitizer compositions (A) and (B) the magnesium ion source may be magnesium ion from an anionic surfactant, if present, in excess of that required for surfactant functionality, or may be supplied separately by a magnesium salt different from the anionic surfactant, such as magnesium sulfate or other water soluble or dispersible magnesium compound. The magnesium ion source is useful for stabilizing foams when the sanitizer compositions contain or are applied in hard water and, in some embodiments of the invention, also assist in maintaining the surfactant system in a liquid state under use conditions.
In preferred embodiments of the invention, the magnesium ion source is present in the sanitizer compositions by addition to the retention aid concentrates, by preadmixture with any of the surfactants, or by addition to the sanitizer compositions when formed by admixture of the concentrates and antimicrobial agents, the latter especially respecting use of antimicrobial agents that are active at acidic pH. The magnesium ion source is added in an amount effective to stabilize resultant foams or films of the sanitizer compositions against degradation in the presence of hard water, for example when hard water is used to prepare, dilute or apply the sanitizer compositions.
The amounts of ingredients in the sanitizer compositions (A) and (B) are based on total weight of the compositions and represent compositions as used. However, as indicated above and as further described hereinafter, the compositions may also be prepared as concentrates for dilution at time of use, in which case the amounts of ingredients will be in ratios represented by the amounts described above but in higher concentrations.
Accordingly, a primary aspect of the invention is a high-retention aqueous sanitizer composition which can be applied to surfaces in a variety of forms: foams, films, fogs, and atomized or sprayed liquids. In preferred embodiments, respecting application as foams, unlike compositions that contain a single surfactant (which tend to be unstable, fall rapidly down a vertical surface, and fail to provide uniform coverage of the surface), the compositions of the invention are retained on the surface and provide more uniform surface coverage. High-retention provides a higher kill of microorganisms with a reduction in the amount of sanitizer composition used.